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From: Peter Zijlstra <peterz@infradead.org>
To: kan.liang@linux.intel.com
Cc: acme@kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org,
	tglx@linutronix.de, jolsa@kernel.org, eranian@google.com,
	alexander.shishkin@linux.intel.com, ak@linux.intel.com
Subject: Re: [PATCH 4/9] perf/x86/intel: Support hardware TopDown metrics
Date: Tue, 28 May 2019 15:32:32 +0200	[thread overview]
Message-ID: <20190528133232.GU2650@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190528125615.GW2606@hirez.programming.kicks-ass.net>

On Tue, May 28, 2019 at 02:56:15PM +0200, Peter Zijlstra wrote:
> On Tue, May 21, 2019 at 02:40:50PM -0700, kan.liang@linux.intel.com wrote:
> 
> > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
> > index e9075d57853d..07ecfe75f0e6 100644
> > --- a/arch/x86/events/core.c
> > +++ b/arch/x86/events/core.c
> > @@ -91,16 +91,20 @@ u64 x86_perf_event_update(struct perf_event *event)
> >  					new_raw_count) != prev_raw_count)
> >  		goto again;

AFAICT, you don't actually need that cmpxchg loop for the metric crud.

> >  
> > -	/*
> > -	 * Now we have the new raw value and have updated the prev
> > -	 * timestamp already. We can now calculate the elapsed delta
> > -	 * (event-)time and add that to the generic event.
> > -	 *
> > -	 * Careful, not all hw sign-extends above the physical width
> > -	 * of the count.
> > -	 */
> > -	delta = (new_raw_count << shift) - (prev_raw_count << shift);
> > -	delta >>= shift;
> > +	if (unlikely(hwc->flags & PERF_X86_EVENT_UPDATE))
> > +		delta = x86_pmu.metric_update_event(event, new_raw_count);
> > +	else {
> > +		/*
> > +		 * Now we have the new raw value and have updated the prev
> > +		 * timestamp already. We can now calculate the elapsed delta
> > +		 * (event-)time and add that to the generic event.
> > +		 *
> > +		 * Careful, not all hw sign-extends above the physical width
> > +		 * of the count.
> > +		 */
> > +		delta = (new_raw_count << shift) - (prev_raw_count << shift);
> > +		delta >>= shift;
> > +	}
> >  
> >  	local64_add(delta, &event->count);
> >  	local64_sub(delta, &hwc->period_left);
> 
> > @@ -1186,6 +1194,9 @@ int x86_perf_event_set_period(struct perf_event *event)
> >  	if (idx == INTEL_PMC_IDX_FIXED_BTS)
> >  		return 0;
> >  
> > +	if (x86_pmu.set_period && x86_pmu.set_period(event))
> > +		goto update_userpage;
> > +
> >  	/*
> >  	 * If we are way outside a reasonable range then just skip forward:
> >  	 */
> > @@ -1234,6 +1245,7 @@ int x86_perf_event_set_period(struct perf_event *event)
> >  			(u64)(-left) & x86_pmu.cntval_mask);
> >  	}
> >  
> > +update_userpage:
> >  	perf_event_update_userpage(event);
> >  
> >  	return ret;
> 
> 
> *groan*.... that's pretty terrible.

  reply	other threads:[~2019-05-28 13:32 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-21 21:40 [PATCH 0/9] TopDown metrics support for Icelake kan.liang
2019-05-21 21:40 ` [PATCH 1/9] perf/core: Support a REMOVE transaction kan.liang
2019-05-21 21:40 ` [PATCH 2/9] perf/x86/intel: Basic support for metrics counters kan.liang
2019-05-28 12:05   ` Peter Zijlstra
2019-05-28 18:20     ` Liang, Kan
2019-05-28 12:15   ` Peter Zijlstra
2019-05-28 18:21     ` Liang, Kan
2019-05-29  7:28       ` Peter Zijlstra
2019-05-29 14:40         ` Liang, Kan
2019-05-29 16:46           ` Peter Zijlstra
2019-05-29  8:14   ` Peter Zijlstra
2019-05-21 21:40 ` [PATCH 3/9] perf/x86/intel: Support overflows on SLOTS kan.liang
2019-05-28 12:20   ` Peter Zijlstra
2019-05-28 18:22     ` Liang, Kan
2019-05-21 21:40 ` [PATCH 4/9] perf/x86/intel: Support hardware TopDown metrics kan.liang
2019-05-28 12:43   ` Peter Zijlstra
2019-05-28 18:23     ` Liang, Kan
2019-05-29  7:30       ` Peter Zijlstra
2019-05-28 12:53   ` Peter Zijlstra
2019-05-28 12:56   ` Peter Zijlstra
2019-05-28 13:32     ` Peter Zijlstra [this message]
2019-05-28 13:30   ` Peter Zijlstra
2019-05-28 18:24     ` Liang, Kan
2019-05-29  7:34       ` Peter Zijlstra
2019-05-29 14:41         ` Liang, Kan
2019-05-28 13:43   ` Peter Zijlstra
2019-05-28 18:24     ` Liang, Kan
2019-05-29  7:54       ` Peter Zijlstra
2019-05-29 14:42         ` Liang, Kan
2019-05-29 16:58           ` Peter Zijlstra
2019-06-04 20:39             ` Liang, Kan
2019-05-28 13:48   ` Peter Zijlstra
2019-05-28 18:24     ` Liang, Kan
2019-05-29  7:57       ` Peter Zijlstra
2019-05-29 14:42         ` Liang, Kan
2019-05-21 21:40 ` [PATCH 5/9] perf/x86/intel: Set correct weight for TopDown metrics events kan.liang
2019-05-28 13:50   ` Peter Zijlstra
2019-05-21 21:40 ` [PATCH 6/9] perf/x86/intel: Export new TopDown metrics events for Icelake kan.liang
2019-05-21 21:40 ` [PATCH 7/9] perf/x86/intel: Disable sampling read slots and topdown kan.liang
2019-05-28 13:52   ` Peter Zijlstra
2019-05-28 18:25     ` Liang, Kan
2019-05-29  7:58       ` Peter Zijlstra
2019-05-21 21:40 ` [PATCH 8/9] perf, tools, stat: Support new per thread TopDown metrics kan.liang
2019-05-21 21:40 ` [PATCH 9/9] perf, tools: Add documentation for topdown metrics kan.liang

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